# How can I set the toc depth so that \chapter's numbering follows \part's numbering?

I use the \documentclass[twoside,11pt]{book}.

My current document yields something like this :

• PART 1
• Chapter 1
• Section 1.1
• Chapter 2
• Section 2.1
• PART 2
• Chapter 3
• Chapter 4
• ...

Instead, what I am trying to do is something like this:

• PART 1
• Chapter 1.1
• Section 1.1.1
• Chapter 1.2
• Section 1.2.1
• PART 2
• Chapter 2.1
• Chapter 2.2
• ...

Is there an easy way to do so ? Thank you for your help.

• Welcome to TeX.SX! Please include a minimal working example (MWE) showing some example parts and chapters as well as the code you used to change the part numbering style. ("PART 1" does not seem to be the default when using the book class.) May 22, 2020 at 19:49

You tell us what you get but not how you get it. You obviously use your own code for changing the ToC layout. Basically I assume that you are just asking about changing the divisional numbering scheme.

% partchapprob.tex SE 545742
\documentclass{book}

\renewcommand{\thechapter}{\thepart.\arabic{chapter}}
\begin{document}
\tableofcontents
\part{One}
\chapter{First}
\section{A section}
\chapter{Second}
\section{Another section}
\part{Two}
\chapter{Ctitle}
\section{Stitle}
\end{document}


In the above MWE the redefinition of the chapter number gives what I think you are after.

It is hard trying to answer a question when you don't know what has been done. --- GOM